1. Field of the Invention
This invention relates to a grid structure for a suspended ceiling, and more particularly to the assembly that interlocks a pair of intersecting cross-beams and a main beam in such grid structure.
2. Background Information
Suspended ceilings having a metal grid structure framework, which supports acoustical panels within rectangular enclosures formed by the grid, are used extensively in commercial and industrial buildings. The grid is suspended from a structure above the ceiling.
Such grid, as is well known, consists generally of parallel extending main beams and intersecting cross-beams. At an intersection, the main beam has a slot in its web which receives a pair of connector clips, with each connector clip, which is on the end of a cross-beam, inserted from opposing sides of the web to form a connector assembly. Such assemblies sometimes interlock the opposing cross-beams to the main beam in a first lock only, but more generally also have a second lock that interlocks the two cross-beams to each other.
Where it is particularly necessary that the assembly resist tension forces that tend to pull the assembly apart, as for instance from seismic events, as well as compressive forces, which tend to push the assembly apart, a first and second lock as referred to above is used. Where the compressive forces arise from fire, it may be desirable to provide expansion means in the assembly to keep the beams directionally in place to retain the panels in the ceiling.
One type of prior art assembly is the stab type, wherein the cross-beam connector clips are inserted into the main beam slot by a longitudinal thrust stab action. Another type of assembly is the hook type, wherein the cross-beam is hooked into the assembly.
Prior art assemblies of the stab type, generally depend on a spring action to engage components to interlock the clips to the main beam in the first lock, and to each other in a second lock. Such spring action is often complicated and does not provide a particularly high degree of resistance to separation from either tension or compressive forces, since the spring components must be made relatively light.
Prior art assemblies of the hook type, without spring action, generally only connect the cross-beams to the main beam in a first lock, without connecting the cross-beams to each other in a second lock. Such hook types are of rigid construction and are relatively simple to make and install, but lack substantial resistance to tension that pulls the assembly apart because of the lack of the second lock.